Positive pressure lid for dialyzer apparatus

ABSTRACT

A cover for sealingly closing the dialysate chamber of an extracorporeal kidney apparatus and providing a flow duct for passing dialyzing fluid from the chamber. A valve in said flow duct to adjust the flow (volume/time) and vary the pressure within the dialyzing fluid compartment.

United States Patent Martinez POSITIVE PRESSURE LID FOR DIALYZERAPPARATUS Jan. 23, 1973 Primary Examinefl-Frank A. Spear; Jr.

[75 Inventor: Felix Jesus Martinez, Palatine, 111.

Attorney-Samuel B. Smith, Jr., W. Garrettson Ellis [73] Assignee: BaxterLaboratories, Morton Grove, d L i Al 22 Filed: Aug. 31, 1970 [57]ABSTRACT [21] Appl' 68294 A cover for sealingly closing the dialysatechamber of an extracorporeal kidney apparatus and providing a 1.8- CI210/494 flow d ct for passing fluid from the chamber. Cl- ..B0ld A alvein said flow duct to adjust the flow [58] Field of Search "210/137, 494,22, 23, 321 (volume/time) and vary the pressure within the dia|yz fl 'dm t t. [56] References Cited g m co par men I UNITED STATES PATENTS 16Claims, 15 Drawing Figures 1,235,625 8/1917 7 Wineman ..210/245 v 1 I2 II i l r i I I I I i 1 H I 24 1 M i f. :1 20 .1 la

FROM PUMP PATENTEDJM 23 1973 saw 1 or 5 FROM PUMP mvsmon W/@ ATTORNEYPATENTEUJAH23 I975 3.712.475

SHEET 2 OF 5 I INVENTOR 60 L ATTORNEY PATENIEDJM|23I915 3.712.475

' sum 3 OF 5 INVENTOR Wmihe z n MM! ATTORNEY PATENTEUJANZB I975 SHEET 14[1F 5 \NVENTOR W Jigsaw zZm/fme ATTORNEY PATENT-EDJM 23 ms 3,712,475SHEETS 0F 5 INVENTOR ATTORNEY POSITIVE PRESSURE LID FOR DIALYZERAPPARATUS The present invention is within the art of artificial kidneyapparatus and concerns particularly a cover member which is received ona canister or outer shell of the apparatus to enclose a dialysatechamber. More particularly, however, the cover member is sealinglyreceived on the canister or outer shell and by provision of a valvedisposed to cooperate with an outflow duct from the dialysate chamberthe internal pressure may be varied.

Various forms of dialysis apparatus are well-known to the art as is thechemical phenomena upon which apparatus of this type is based. However,most of the known apparatus suffer from problems of water diffusionduring dialysis, a condition which, under most circumstances, cannot betolerated. It is this problem which the present invention seeks toovercome by management of the dialysate chamber pressure andconsequently a transmembrane pressure gradient, as will be described.

Briefly, dialysis is carried out in an extracorporeal system and servesto cleanse from a biological fluid, such as blood, various organic andinorganic substances which are harmful to the system; For the purpose ofthis discussion the biological fluid will be considered as being blood.

One form of dialysis apparatus includes a blood flow chamber generallyin the form of an elongated length of plastic tubing which may bewrapped upon a core and a dialysate chamber within which the bloodchamber is disposed and through which a dialyzing fluid or wash solutionis flowed. Byproper' support of the tubing which may be in the form of asemipermeable dialyzing membrane, for example Cuprophanwhich is acellulose base membrane similartov cellophane, throughout its length thedialyzing fluid will be able to flow over a maximum amount of membranesurface area. The flow of blood and dialyzing fluid over each incrementof membrane and on opposite sides of the membrane is preferably keptsteady and continuous, even at the membrane surface where therequirement of flow is most important. In this connection thepresentationof a stationary liquid film at the membrane surface wouldreduce solute diffusion efficiency.

As a consequence of a driving force (chemical concentration gradient)between the moving fluids on either side of the semipermeable membrane apassive physical difi'usion'of organic and inorganic substances willoccur. To maintain the concentration gradient, if the dialyzing fluid isto becontinuously, circulated within a recirculating system, it ispreferable to continuously drain a small volume of dialyzing fluid andto replenish the drained volumewith fresh fluid. This is well-known. I

Ultrafiltration also occurs during solute diffusion. Ultrafiltration isa phenomena which is not totally un' derstood. Further, a completediscussion of what is thought to be the scientific principle and reasonsfor the occurrence of water diffusion from blood plasma is outside thescope of this invention; However, it is thought that ultraflltration isa consequence or a function of many dialyzer characteristics. Thus,ultraflltration is determined by,'among other considerations, thetransmembrane pressure gradient, area of dialyzer and perfusion flowrate, water permeability of the membrane and boundary layer conditions.Of these, probably the most important consideration is the transmembranepressure gradient.

The mean transmembrane pressure gradient, in a coil dialyzer, is of acomplex nature. It is probably the summation of a multitude ofpressures. Assuming that the blood path behaves like a rigid system,then pressure drop has a linear function following Poiseiulles equation:

IZpL

vAP:VV XQIal where p, is the viscosity of the test solution indynessec/cm, Land W are the length and width of the dialyzer blood pathin cm, H is the blood passage thickness in cm. and Q, is the testsolution flow rate in cm second. Then for a given set of steady stateconditions the pressure drop across the dialyzer blood compartment canbe. approximated as the difference between the inlet and outlet pressuremeasurements.

. AP: in ost The mean pressure across the blood compartment would be theaverage pressure between inlet and outlet of the dialyzer bloodcompartment TP= P,,,+P,,, /2 The mean pressure across the dialysatecompartment would be the average pressure between the inlet and outletdialyzer dialysate compartment.

w (P5,P 5

' m in mm. Hg.

2 dialysate blood The blood osmotic pressure gradient, although veryimportant, is not considered in this version of transmembrane pressurecalculation. where IP= Transmembrane pressure in mml-lg.

P =Pressure inlet (blood path) mml-lg.

B5,, =Pressure outlet (blood path) mml-lg.

n ==Pressure dialysate inlet mml-lg.

P f=Pressure dialysate outlet mmllg.

Following this hypothesis, one can modify ultrafiltration bymanipulating transmembrane pressure. In actual tests by increasing theresistance at the dialysate outflow passage by manipulation of valvingstructure thereby to decrease flow the hydrodynamic pressure of thedialysate compartment may be increased. Since the pressure within theblood compartment is greater than the pressure within the dialysatecompartment under atmospheric conditions an increase in dialysatechamber pressure will serve to diminish the transmembrane pressuregradient.

The amount of water diffusion would appear to be directly dependent, inpart, upon the transmembrane pressure. While, as stated, the phenomenais not clearly understood there appeared, in tests, to be a dialysatechamber pressure value at which for any constant perfusion flow thevolume of water diffusion became TP: (Page...

smaller and then leveled to a relatively constant volume. Thus, for anyone perfusion flow rate there appears to be some optimal pressure abovewhich there is no significant reduction in ultrafiltration.

It is believed that this is a result of a reduced efficiency of thepositive dialysate pressure in further reducing the transmembranepressure gradient. In this connection, as the dialysate pressure isincreased, a pressure increment is transmitted to the blood compartment.Therefore, control of ultrafiltration by means of pressurized dialysisis believed to be self-limiting at high dialysate chamber pressure.

A significant loss in the volume of blood during dialysis cannot betolerated. This is because a very large percentage of chronichemodialysis patients receive through transfusion procedures little orno blood during their therapeutic treatment. Thus, maximum bloodrecovery from the dialyzer is of paramount importance.

By the present invention the transmembrane pressure gradient may bereduced by pressurizing the dialysate chamber thereby to decrease thevolume of water diffused from the plasma within the blood chamber intothe dialysate compartment. This has been accomplished without detrimentto the solute removal efficiency of the dialyzer.

In accordance with this aspect of the present invention there isprovided a cover adapted for receipt upon the outer shell or canisterdefining the dialysate chamber of a coil-type dialyzer. However, it isto be clearly understood that the principle disclosed within thisinvention is applicable to dialyzers of types other than the coil type.The cover is provided with means to secure the same in a sealed manneron the outer shell or canister thereby to permit the build-up of apositive pressure within the dialysate chamber. The cover is formed witha passage through which dialyzing fluid passes from the chamber to berecirculated, as choice determines, and a valve mechanism operable inconjunction with the passage to change the resistance to flow thereby todevelop or release pressure in the dialysate chamber. A pressureincrease will simultaneously diminish the transmembrane pressuregradient.

In one form of the present invention the cover may be formed as anintegral unit while in a slightly modified form of the present inventionthe cover may include a plate member of substantially flat constructionand an annular ring member cooperable with the plate and serving as amount for the latter on the outer shell or canister. The plate, as thecover described above, includes in conjunction with the dialysateoutflow passage valving structure. The ring is provided with a pluralityof cutouts for the introduction of one or more flexible tubes forming apart of the blood circulatory system and for connecting the bloodchamber therein.

In accordance with a further aspect of the present invention, a guideblock is formed within the cover to both receive and accommodate as wellas to grip a plurality of flexible tubes connecting the bloodcompartment into the blood circulating system. In this connection theguide block is formed by a member capable of pivotal movement into andout of as well as up and down within a cutout portion of the cover andalong the longitudinal axis of the cover when receiving the plurality oftubes. The block includes a plurality of semicircular cutouts formed tocooperate with complementary cutouts within a shoulder to positivelygrip the several tubes in position.

In an additional aspect of the present invention there is means tomeasure the pressure within the dialysate chamber. To this end there isprovided a port in communication with the chamber and a nipple mountadapted to connect a form of pressure measuring gauge.

There has thus been outlined rather broadly the more important featuresof the present invention in order that the detailed description thereofthat follows may be better understood and in order that the presentcontribution to the art may be better appreciated. There are, of course,additional features of the present invention that will be describedhereinafter and which will form the subject of the claims appendedhereto. Those skilled in the art will appreciate that the conceptionupon which this disclosure is based may readily be utilized as a basisfor the designing of other structures for carrying out the severalpurposes of the invention. It is important, therefore, that the claimsbe regarded as including such equivalent construction as do not departfrom the spirit and scope of the invention.

In order that the invention may be more readily understood the same willnow be described in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a view in elevation, partly broken away and in section, of acoil dialyzer and the dialyzer cover;

FIG. 2 is a side elevation of the dialyzer cover and partially showingexploded therefrom a canister or dialyzer shell to which the cover issealingly mounted;

FIG. 3 is a top plan view of the dialyzer cover;

FIG. 4 is a bottom plan view of the dialyzer cover;

FIG. 5 is a vertical sectional view as seen along the line 5-5 of FIG. 3showing the flow port through the dialyzer cover and a valve member inthe port;

FIG. 6 is a view in perspective of a portion of the dialyzer cover and agate portion for supporting one or more fluid lines;

FIG. 7 is a partial vertical section through the dialyzer coverillustrating the manner of mounting on the canister or dialyzer shell;

FIGS. 8 and 9 are partial vertical sections through the dialyzer covergate illustrating in sequence the manner in which the fluid lines arepositioned and supported;

FIG. 10 is a horizontal section as seen along the lines 10-10 in FIG. 5illustrating the port valve and that through rotation the volume of flowthrough the port may be changed;

FIG. 11 is an exploded perspective of a modified fonn of the dialyzercover and showing a lip portion of a canister or shell;

FIG. 12 is a breakaway view in elevation illustrating the positioning ofthe cover on the canister or shell;

FIG. 13 is a bottom plan view of the dialyzer cover less annular ring asseen in FIG. 1 1;

FIG. 14 is a vertical section as seen along the line 14-14 in FIG. 13and including in section a portion of the annular ring and canister orshell; and

FIG. 15 is a view similar to that of FIG. 12 illustrating the manner ofreceiving the cover, by clamping members, on the canister or shell.

A coil dialyzer of the type adapted to utilize the dialyzer cover of thepresent invention may be seen in FIG. 1. While the dialyzer constructionand operation per se are not important to an understanding of thisinvention it is considered important to develop a background so that thepresent invention may be more clearly understood.

In an extracorporeal device, such as is shown in FIG. 1, there is.passive physical diffusion of unwanted organic and inorganic substancesacross a semipermeable membrane as a consequence of driving force(chemical concentration gradient) from two moving fluids on opposedsides of the semipermeable membrane. To carrying out with acceptableefficiency the difiusion of substances from the blood it is desirable toprovide maximum exposed membrane surface area to the flow of dialyzingfluid. At the same time, however, the membrane which may be in the formof an extended length of tube necessarily needs support throughout thislength. This is particularly true in the coil-type dialyzer as is shownin -FIG. 1. Therefore, as generally illustrated, an extended length ofsupported membrane tub,- ing is wrapped upon a core 12 within the areabounded by a canister or shell 14. The particular sup port structure isnot shown in any detail since its construction is outside the scope ofthis invention. However, it is to be kept in mind that it serves to bothsup-' port the membrane and allow a maximum of exposed membrane surfaceto the flow of dialyzing fluid.

While notshown the membrane is connected to an a bottom wall 20 of thedialyzer assembly. By the provision of, for example, a somewhatconically shaped diverter plate 22 and annular perforated ring 24 thedialyzing fluid may be uniformly introduced into the assembly thereby toflow uniformly over the total membrane surface toward the dialyzingfluid outflow port.

In order that there may be a constant recirculation of dialyzing fluidin a closed system the fluid passed from the outflow port of thedialyzing chamber into a reservoir formed by a container'26JAs shown,the reservoir container maybe supported by surface 28. Any particularsystem for this purposemay be utilized. Such systems are well-known inthe art. However, since dialysis efficiency gradually diminishes withthe action of the apparatus, because of the diffusion gradientprogressively falling off, through operation, it is appropriate to bothdrain off a small portion of the dialyzing fluid and to replenish itwith an equivalent amount of fresh dialyzing fluid thereby to maintainthe diffusion gradient. In this connection the reservoir may be providedwith an overflow determining the height of the reservoir or a tap orspout 30 within the wall of container 26.

- A dialyzing fluid outflow port is formed within the dialyzercover,generally identified, by the numeral 50, which will now be described.

The dialyzing cover is illustrated as having a substantially flat uppersurface 52 and generally of circular construction throughout. Dependingfrom the peripheral region of the cover is an annular ring 54 providinga mounting surface for the cover on the canister or shell 14 whichisformed with an upper outturned lip 56.

The cover 50 may be formed of any material which may be fabricated as bymolding and thereafter capable of being machined. The material of thecover should also provide a sturdy construction thereby to be a rigidassembly for a dialyzer unit. The construction also will be of the typecapable of maintaining desired pressure conditions within an enclosedspace. Generally, any of the commonly used metals, such as aluminum, orany of the widely used plastics, such as polypropylene, high densitypolyethylene, Lucite, among others, may be employed. If the cover isdesirably to be transparent or translucent one of the plastic materialsmay be preferred.

As is illustrated, the cover 50 is mounted so that a bottom portion ofthe annular ring 54 rests upon the upper surface of lip 56. A furtherextending annular ring 58 is received within the upper opening of theshell 14 to position properly the cover. An O-ring 60 carried by theannular portion 54 serves to provide an airtight seal for the shellinterior or dialysate chamber in which the dialyzing membrane isdisposed. A plurality clamping assemblies including a post 62 having acentral longitudinal bore 64, an elongated threaded bolt 66 whichextends throughout the bore and which terminates in a foot portion 68,as well as a knurled thumb screw are integral with or otherwise carriedby the cover at spaced locations therearound. Preferably there may bethree or four assemblies for the purpose of securely and sealinglymounting the cover 50. In assembly, the several feet 68 are receivedunder the shell lip 56 thereby tightening the knurled screw 70 tocompress the O-ring 60 between the annular ring and lip 56.

A plurality of projections 72 are carried by or integral with theunderside of the cover (FIG. 4). The projections serve to provide withthe perforated annular ring 24 supporting confinement for the wrappedmembrane 10 within the dialysate chamber.

The body of the cover 50 provides within a peripheral sector a somewhattrapezoidal shaped cutout 74.'The amount of cutout within an upperportion is greater than that within the lower portion thereby to providea shoulder 75. A guide block 76 is mounted for swinging movement intoand out of the opening 74 as well as longitudinal movement within theopening between the FIG. 8 and 9 positions. The need to accommodate andprovide for this movement will become apparent as the descriptioncontinues. The guide block is dimensioned to be complementary with theshoulder and provide a smooth peripheral outer surface of the cover asin FIG. 6.

As is also shown in FIG. 6 a pair of hinges 78 and 80 are carried by theguide block and cover body, respectively. The hinges intercooperate bythe provision of pin being received within the turned extremity 84 ofbinge 78. A lock plate 85 and cooperating knurled screw 86 are carriedat the opposite side of the guide block to secure the latter in theclosed position.

Both the shoulder 75 and the inside surface of the guide block carry aplurality of cooperating semicircular cutouts 88 and 90 forming a seriesof circular openings 92. These openings accommodate the tubes 94 whichserve to connect the diffusion membrane into an extracorporealcirculatory blood path. The provision of a set or sets of two openings92 permit a single or dual wrapped diffusion membrane to be connectedinto the system.

As has been discussed, the guide block is movable between FIG. 8 andFIG. 9 positions. This movement permits the several tubes 94 to bepartially supported by the semicircular cutouts 88 and 90 (FIG. 8)whereupon the guide block is lowered (FIG. 9) so that the tubes aregripped within the openings 92. The tubes could not be otherwise grippedsolely by pivotal closure of the guide block. Thus, if the tubes were tobe received within the cutouts 88 they, upon closure of the guide block,would be pinched.

A port or channel 96 is formed within the cover body. This port orchannel provides for discharge of dialyzing fluid from the dialysatechamber into the reservoir 26. A spout or splash shield 98 is mounted atthe end of the port to direct the flowing dialyzing fluid into thereservoir 26.

The channel includes a horizontal passage 100 and a communicatingvertical passage 102. A rotary valve 104 is disposed within the verticalpassage and upon rotation may provide either an increase or decrease inthe volume of outflow of dialyzing fluid.

The valve includes a generally cylindrical lower shaft portion 106having an opening 108 in one wall portion of a size substantially equalto the cross-sectional size of the horizontal passage. The upper shaft110 terminates in a hand gripping member to enable the operator torotate the valve shaft with relative ease thereby to adjust the flow ofdialyzing fluid. A U- shaped clamp plate 112 intercooperates with anannular cutout 114 in the valve shaft to allow rotation of the valvewithin the port 96 yet at the same time to prevent the valve from beingwithdrawn from the passage 102.

In operation, the cover is mounted as described and blood is caused topass through the membrane or blood chamber. Simultaneously dialyzingfluid is introduced into the dialysate chamber and because of amaintained diffusion gradient across the membrane the diffusion ofunwanted organic and inorganic substances continues. Usually thepressure within the blood chamber is in excess of the pressure withinthe dialysate chamber thereby creating a pressure gradient across themembrane with consequent ultrafiltration or diffusion of water to thearea of lower pressure. By proper manipulation of the valve 104 apositive pressure may be developed within the dialysate chamber therebyto decrease the transmembrane pressure gradient and decrease the amountof water diffusion from the plasma. The dialysate chamber pressure maybe read on a pressure meter 116 mounted by a connector 118 communicatingwith the interior of the dialysate chamber thereby to maintain thechamber at the desired pressure.

In a somewhat modified form of the invention, referring specifically toFIGS. 11 15, the cover 200 is formed of a plate section 202 and anannular ring section 204. The ring section 204 is substantially similarin construction to the depending ring section 54 of cover 50. Similarly,the plate section 202 is substantially similar to the correspondingportion of cover 50.

The dialyzing fluid outflow port is defined by a plurality of passages208 214 in communication with the dialysate chamber. By the provision ofpassages of varying size the volume of flow through the port and thechamber pressure may be controlled with some 'degree of precision. Acover or shield 206 provides an enclosure over the outflow port andserves to direct with limited splashing the dialyzing fluid into thefluid reservoir.

A control member 216 is supported for rotation by the shield 206 and thebottom surface of plate section 202. The control is defined by a shaft218 which carries a knob 220 at one end and a curved, flat plate 222 atthe other. As may be apparent proper positioning of the plate coveringone or more parts of openings 208 214 will effect the flow volume fromthe dialysate chamber.

The ring 204 and plate 202 are adapted to be mounted upon the canisteror shell 14 of the coil dialyzer 10. To assure proper sealing of thedialysate chamber the annular ring 204 includes an O-ring 230 whichrests upon the lip 56 while a second O-ring 232 provides a seal at thejunction between the annular ring and the plate 202. As with the cover50 a projection 234 on the annular ring serves to position the cover 200upon the shell 14.

A plurality of clamping members 236 are supported in spaced relation onthe plate 202. As shown, the clamps are mounted by supporting lu'gs 238which are frictionally or otherwise received within openings 240 formedin the plate 202 at approximately spaced locations. The several clampsare identical in construction and therefore only one such clamp isillustrated. The clamp comprises a bifurcated body 242 having a base 242into which the lug 238 is joumelled for rotation. The clamp throughappropriate mounting is also capable of pivotal movement about the lug.An arm 244 having a finger gripping end 246 is mounted on the body andcapable of being pivoted about the body. Through manipulation of thebody and arm the finger gripping end 246 may be received under the lip56. Movement of body 242 from a raised pivotal position to the positionof FIG. 15 serves to securely grip the lip thereby to positively mountthe cover 200.

A nipple 248 supported by the plate 202 in communication with a passage250 connecting the dialysate chamber is adapted to receive a pressuregauge, such as gauge 1 16, for the same purpose.

Whereas the cover 50 included a guide block 76 for gripping the severalflexible tubes 94, the ring 204 in the present modification provides aplurality of channels 252 to accommodate the tubes. The O-ring 232cooperates with the channel surfaces to grip the tubes without pinching.

From the foregoing it will be seen that in accordance with the presentinvention there is provided a dialyzer cover which performs the objectsand provides advantages not heretofore achieved in dialysis.

' Having described the invention with particular reference to thepreferred forms thereof, it will be obvious to those skilled in the artto which the invention pertains, after understanding the invention, thatvarious changes and modifications may be made therein without departingfrom the spirit and scope of the invention as defined by the claimsappended hereto.

Having described the invention, what is claimed is:

1. A cover for dialyzer apparatus having a dialysate chamber throughwhich dialyzing fluid is circulated continuously thereby to be incontact over a surface within said chamber of a blood compartmentadapted to confine a blood stream and formed by a membrane providing asemipermeable interface between said dia lyzing fluid and blood throughwhich because of a concentration gradient unwanted organic and inorganicsubstances diffuse from the blood into said dialyzing fluid, said covercomprising a body portion, said body portion including a dish-shapedmember and a annular member, means on said body portion adapting saidcover for receipt on said apparatus thereby to isolate said chamber fromambient conditions, means including a plurality of substantiallyradially disposed grooves in an upper surface of said annular memberjuxtaposed to said dish-shaped member when said members are receivedtogether for permitting unrestricted access of at least an inlet and anoutlet tube into said chamber thereby to connect said blood compartmentin an extracorporeal fluid system, means carried by one of said membersto provide a seal therebetween, port means including a plurality ofpassages'formed within said body providing a port through which saiddialyzing fluid is passed, and means cooperable with said port meansforvarying through rotational adjustment the effective port area to adjustthe volume of flow of dialyzing fluid through said port means thereby tovary dialysate chamber pressure and the transmembrane pressure gradient.

2. The cover of claim 1 wherein said passages are of varyingcross-sectional diameter.

3. The cover of claim 1 comprising a shield over the end of said portmeans to prevent splashing of said dialyzing fluid exiting said portmeans.

4. The cover of claim 3 comprising a post, said post extending throughsaid shield and said body and mounted for rotary movement, and saidadjustable means comprising a plate carried by one end of said post andmovable with said post thereby to adjust said volume of flow.

5. The cover of claim 4 wherein said cooperable means includes a flatplate mounted for rotation substantially in a plate including entranceto said port means thereby through movement to adjust the effectiveopening of the same, and means supported by said cover for moving saidplate. 1

6. The cover of claim 1 including means carried by one of said apparatusand body to provide a fluid seal between said body and apparatus whenreceived.

7. The cover of claim 6 wherein'said sealing means is an O-ring.

8. The cover of claim 1 including means on said body adapted to mount agauge to monitor chamber pressure.

9. A cover for dialyzer apparatus having a dialysate chamber throughwhich dialyzing fluid is circulated continuously thereby to be incontact over a surface within said chamber of a blood compartmentadapted to confine a blood stream and formed by a membrane roviding asemipermeable interface between said diayzing fluid and blood throughwhich because of a concentration gradient unwanted organic and inorganicsubstances diffuse from the blood into said dialyzing fluid, said covercomprising a body portion, said body portion being provided with aperipheral cutout of substantially trapezoidal shape and having a lowershoulder means for permitting access of at least an inlet and an outlettube into said chamber thereby to connect said blood compartment in anextracorporeal fluid system, said means including a guide block, saidguide block. having a plurality of substantially longitudinally disposedgrooves for cooperating with a like plurality of grooves formed in saidshoulder thereby to define a substantially circular opening throughwhich said tubes are unrestrictedly received, means on said body portionadapting said cover for receipt on said apparatus thereby to isolatesaid chamber from ambient conditions, port means including a pluralityof passages formed within said body providing a port through which saiddialyzing fluid is passed, and means cooperable with said port means forvarying through rotational adjustment the effective port area to adjustthe volume of flow of dialyzing fluid through said port means thereby tovary dialysate chamber pressure and the transmembrane pressure gradient.

10. The cover of claim 9, wherein one of said plurality of passages isdefined by a longitudinal substantially cylindrical opening through saidbody and a second of said plurality of passages being defined by atransverse communicating bore.

11. The cover of claim 10 wherein said adjustable means comprises asubstantially cylindrical cup-shaped element received for rotationwithin said opening, said cup-shaped element having an opening withinone wall of a size substantially equal to the size of said transversebore, and means in said cover for rotating said element to vary theeffective port opening.

12. The cover of claim 11 including means to maintain the verticallongitudinal disposition of said cupshaped element yet permit rotationof said element within said opening.

13. The cover of claim 9 comprising hinge means allowing movement ofsaid guide block between a normal lowered position within saidperipheral cutout to a raised position at which through pivotal movementout of said peripheral cutout said tubes may be received by I said guideblock grooves whereupon said guide block is redisposed in the normalposition at which said tubes are positioned within said circularopenings.

14. The cover of claim 9 comprising a shield over the end of said portmeans to prevent splashing of said dialyzing fluid exiting said portmeans.

15. The cover of claim 9 including means carried by one of saidapparatus and body to provide a fluid seal between said body andapparatus when received on the latter.

16. The cover of claim 9 including means on said body adapted to mount agauge to monitor chamber pressure.

t i '3 i

1. A cover for dialyzer apparatus having a dialysate chamber throughwhich dialyzing fluid is circulated continuously thereby to be incontact over a surface within said chamber of a blood compartmentadapted to confine a blood stream and formed by a membrane providing asemipermeable interface between said dialyzing fluid and blood throughwhich because of a concentration gradient unwanted organic and inorganicsubstances diffuse from the blood into said dialyzing fluid, said covercomprising a body portion, said body portion including a dishshapedmember and a annular member, means on said body portion adapting saidcover for receipt on said apparatus thereby to isolate said chamber fromambient conditions, means including a plurality of substantiallyradially disposed grooves in an upper surface of said annular memberjuxtaposed to said dish-shaped member when said members are receivedtogether for permitting unrestricted access of at least an inlet and anoutlet tube into said chamber thereby to connect said blood compartmentin an extracorPoreal fluid system, means carried by one of said membersto provide a seal therebetween, port means including a plurality ofpassages formed within said body providing a port through which saiddialyzing fluid is passed, and means cooperable with said port means forvarying through rotational adjustment the effective port area to adjustthe volume of flow of dialyzing fluid through said port means thereby tovary dialysate chamber pressure and the transmembrane pressure gradient.2. The cover of claim 1 wherein said passages are of varyingcross-sectional diameter.
 3. The cover of claim 1 comprising a shieldover the end of said port means to prevent splashing of said dialyzingfluid exiting said port means.
 4. The cover of claim 3 comprising apost, said post extending through said shield and said body and mountedfor rotary movement, and said adjustable means comprising a platecarried by one end of said post and movable with said post thereby toadjust said volume of flow.
 5. The cover of claim 4 wherein saidcooperable means includes a flat plate mounted for rotationsubstantially in a plate including entrance to said port means therebythrough movement to adjust the effective opening of the same, and meanssupported by said cover for moving said plate.
 6. The cover of claim 1including means carried by one of said apparatus and body to provide afluid seal between said body and apparatus when received.
 7. The coverof claim 6 wherein said sealing means is an O-ring.
 8. The cover ofclaim 1 including means on said body adapted to mount a gauge to monitorchamber pressure.
 9. A cover for dialyzer apparatus having a dialysatechamber through which dialyzing fluid is circulated continuously therebyto be in contact over a surface within said chamber of a bloodcompartment adapted to confine a blood stream and formed by a membraneproviding a semipermeable interface between said dialyzing fluid andblood through which because of a concentration gradient unwanted organicand inorganic substances diffuse from the blood into said dialyzingfluid, said cover comprising a body portion, said body portion beingprovided with a peripheral cutout of substantially trapezoidal shape andhaving a lower shoulder means for permitting access of at least an inletand an outlet tube into said chamber thereby to connect said bloodcompartment in an extracorporeal fluid system, said means including aguide block, said guide block having a plurality of substantiallylongitudinally disposed grooves for cooperating with a like plurality ofgrooves formed in said shoulder thereby to define a substantiallycircular opening through which said tubes are unrestrictedly received,means on said body portion adapting said cover for receipt on saidapparatus thereby to isolate said chamber from ambient conditions, portmeans including a plurality of passages formed within said bodyproviding a port through which said dialyzing fluid is passed, and meanscooperable with said port means for varying through rotationaladjustment the effective port area to adjust the volume of flow ofdialyzing fluid through said port means thereby to vary dialysatechamber pressure and the transmembrane pressure gradient.
 10. The coverof claim 9, wherein one of said plurality of passages is defined by alongitudinal substantially cylindrical opening through said body and asecond of said plurality of passages being defined by a transversecommunicating bore.
 11. The cover of claim 10 wherein said adjustablemeans comprises a substantially cylindrical cup-shaped element receivedfor rotation within said opening, said cup-shaped element having anopening within one wall of a size substantially equal to the size ofsaid transverse bore, and means in said cover for rotating said elementto vary the effective port opening.
 12. The cover of claim 11 includingmeans to maintain the vertical longitudinal disposition of saidcup-shaped element yet permit rotation of said element within saidopeniNg.
 13. The cover of claim 9 comprising hinge means allowingmovement of said guide block between a normal lowered position withinsaid peripheral cutout to a raised position at which through pivotalmovement out of said peripheral cutout said tubes may be received bysaid guide block grooves whereupon said guide block is redisposed in thenormal position at which said tubes are positioned within said circularopenings.
 14. The cover of claim 9 comprising a shield over the end ofsaid port means to prevent splashing of said dialyzing fluid exitingsaid port means.
 15. The cover of claim 9 including means carried by oneof said apparatus and body to provide a fluid seal between said body andapparatus when received on the latter.
 16. The cover of claim 9including means on said body adapted to mount a gauge to monitor chamberpressure.